Abstract
This paper describes the development of the electromagnetic force sensor which can be used to measure both the displacement of its probe end from the measured surface and the normal direction of the surface. The inclination of the sensor axis from the normal direction can be obtained by measuring the three components of the magnetic attraction force which is applied to the magnet at the end of the probe, based on the fact that the force is perpendicular to the surface. In the preceding report, one of the authors proposed a magnetic force sensor with a permanent magnet. In this case, however, the diameter of the magnet should be large enough to get a sufficient force. Therefore, there are some problems as follows: (1) It is difficult to measure intricate configurations of the surface because of collision of the magliet to the surface. (2) The error of measurement is large at a point where the radius of curvature is small. (3) The weight of the magnet affects the measurement of the magnetic force. In the present work, the permanent magnet is replaced by an electromagnet, and the probe end is made sharp. Moreover, it is found that the preciseness of measurement can be improved by comparing the sensor outputs when the coil current is switched on and off, because the influence of the self-weight of the probe and the drift noise can be eliminated.
